How can I tell if HD is set up for RAID?

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Level 1

1 points

How can I tell if HD is set up for RAID?

I received an external Western Digital 4TB drive with some files on it and I'm trying to tell if the drive is already set up for RAID or not. The company I received it from couldn't tell me and according to the WD box, it's "pre-configured for maximum capacity (RAID 0)". However, when I go into Disk Utility to view the drive, it says the capacity is only 1.8T.

I little more detail... In Disk Utility the left window shows the drive named, "1.8 TB WD My Book Media". Total capacity 1.8TB
S.M.A.R.T. Status: Not Supported
Partition Map Scheme: GUID Partition Table

...In the Partition window it looks like a single partition. Again, Size: 1.8 TB, Available space: 1.1 TB.

Does this make sense? Sorry, I'm not familiar with RAID drives and how they're set up and used. Any help with this would be greatly appreciated.

I'm just trying to find if this drive is in fact set up as a RAID drive and if so, is it mirroring to the second drive in the enclosure? or not? And if not why does it say that the drive is only 1.8 TB?

Sorry for the rambling.

Thanks.

Mac Pro, Mac OS X (10.5.6)

Posted on Mar 8, 2010 12:09 PM

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Answer 1

Kappy

Level 10

362,007 points

Mar 8, 2010 12:29 PM in response to athom75

There is no such thing as a "RAID" drive. Any drive can be used in a RAID array. A single drive is not a RAID drive. It is simply a single drive. When multiple drives are combined into an array via software and/or hardware then one has a RAID array.

Now as far as I can determine WD does not make a single drive larger than 2 TBs. Formatted the drives will contain roughly 1.8 TBs. WD does make a My Book version that has two 2 TB drives that can be configured into a striped RAID array that will provide 4 TBs of storage. I don't know if the product is pre-configured as a RAID array or if you must configure it as such using Disk Utility. For the latter you must first partition and format each drive then use the RAID tab option of DU to set up the RAID array. Select Disk Utility Help from the DU Help menu and search for "raid" to get the help articles on how to set up striped or mirrored RAIDs.

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Answer 2

athom75 Author

Level 1

1 points

Mar 8, 2010 12:45 PM in response to Kappy

The box says it's pre-configured for RAID 0, which I guess means that I would have 4TB of space on my 4TB drive (or more specifically two 2TB drives). If this is the case, 1) why is Disk Utility telling my that it's total capacity is only 1.8 TB? And 2), if there are 2 drives being utilized, shouldn't I see 2 drives mounted on my desktop? I only see a single drive.

I guess I just completely confused why the box would say I have a 4TB "Dual-drive Storage System with RAID", but when I look at the capacity of the drive(s) it says I only have 1.8TB. Where are my other 2 TB's! 🙂

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Answer 3

athom75 Author

Level 1

1 points

Mar 8, 2010 12:52 PM in response to athom75

Oh, one more idea. Let's say that this 4TB drive was set up for RAID 1 – again I was given this drive with files already on it and no one seems to be able to tell me if it was configured for RAID or no.

So again if it were set up for RAID 1, I really only have 2TB of storage to use – the other 2TB being a mirror. If drive 1 was mirroring to drive 2, would drive 2 mount on my desktop? Would I be able to see drive 2 in Disk Utility? How can I confirm it's actually mirroring my data?

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Answer 4

Kappy

Level 10

362,007 points

Mar 8, 2010 2:41 PM in response to athom75

A RAID array is treated as a separate volume mounted on your Desktop. The two drives making up the array do not appear on the Desktop but will appear in Disk Utility. You will find three devices listed in DU. Each drive is listed separately as a physical device containing a ghosted logical device named as a "RAID slice." Then there is the third entry which is the RAID array volume with whatever name you assigned to it. If you configured a striped array this volume will have slightly less than 3.6 GBs listed as the size. A mirrored array would show slightly less than 1.8 GBs as the size.

Whatever problems you are having I suggest you start with the user manual that came with the product. If that doesn't help you then call WD tech support for help.

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Answer 5

athom75 Author

Level 1

1 points

Mar 8, 2010 2:52 PM in response to Kappy

Hmmm, since I'm only seeing a single drive in DU and it's only 1.8TB, maybe there IS something wrong with the enclosure not allowing me access to all the disk space. I'll see what WD has to say.

Thanks, Kappy for all the info.

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